Kinematical structure of the circumstellar environments of galactic B[e]-type stars ^*

Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany

Corresponding author: fzickgraf@hs.uni-hamburg.de

Received: 27 September 2002
Accepted: 19 June 2003

Abstract

High resolution line profiles are presented for selected forbidden and permitted emission lines of a sample of galactic B[e]-type stars. The spectral resolution corresponds to 5-7 km s^-1  with the exception of some line profiles which were observed with a resolution of 9-13 km s^-1. All Hα profiles are characterized by a narrow split or single emission component with a width of ~ km s^-1 (FWHM) and broad wings with a full width of ~ km s^-1. The Hα profiles can be classified into three groups: double-peaked profiles representing the majority, single-peaked emission-line profiles, and normal P Cygni-type profiles. Likewise, the forbidden lines exhibit in most cases double-peaked profiles. In particular, the majority of stars shows split [O i]λ6300 Å. Double-peaked profiles are also found in several stars for [N ii]λ6583 Å and [Fe ii]λ7155 Å although these lines in many stars exhibit single-peaked emission profiles. The split forbidden line profiles have peak separations of as little as ~10 km s^-1, and were therefore only discernible for the first time in the high-resolution spectra. The ratio of violet to red emission peak intensities, , is predominantly smaller or equal to 1. Theoretical profiles were calculated for the optically thin case. A latitude-dependent stellar wind with a radial expansion and a velocity decreasing from the pole to the equator was adopted. This configuration can produce split line profiles if viewed under some angle with respect to the line of sight. In addition an equatorial dust ring with various optical depths was assumed. It can explain line asymmetries observed in some stars. Moreover, the  ratios can be understood in terms of this model. The comparison of the observed line profiles with the models thus confirms the assumption of disk-like line-formation regions as commonly adopted for B[e]-type stars.